The invention relates more particularly to a recording device for the electrostatic reproduction of an image including a comb of electrodes, counter electrodes and supply leads for the electrodes, the comb of electrodes including at least two rows of electrodes insulated from another, which are disposed as conductive tracks on a carrier plate.
In the technique for facsimile reproduction, an image is scanned in a scanning device dot-by-dot and line-by-line, by means of a photo-electric scanning member, and the brightness information of the image dots is transformed into an electric image signal.
The image to be copied may be a printed or type-written document, a handwritten text, or also a graphical illustration.
In a known recording apparatus the image signal controls a recording member, which in the case of an electrostatic reproduction, consists of a comb of electrodes and a plurality of counter electrodes. Between the comb of electrodes and the counter electrodes there passes a recording medium, which is composed of a base layer of medium conductivity, and of a dielectric layer facing the comb of electrodes.
Electrostatic recording is effected by transferring point charges to the dielectric layer of the recording medium, the point charges being created by a spark discharge between an electrode and the associated counter electrode.
On the recording medium there is created an electrostatic charge pattern, which corresponds to the information scanned from the image.
Following recording, the latent charge image is developed by application of toner materials, and changed to a visible image, which may be fixed, for example, by heat treatment. The developed and fixed recording medium is the desired copy of the image.
The comb of electrodes of the recording medium includes a multiplicity of individual electrodes. In order to obtain a high degree of printing density and a fine resolution during recording, the individual electrodes are disposed closely to one another. However, they must be insulated from one another so that the electrodes can be selectively controlled.
The comb of electrodes preferably includes two parallel rows of electrodes insulated from one another, which extend over the whole width of the recording medium. The electrodes of one row are aligned very precisely with respect to the separation distance of two respective electrodes of the other row. Precise positioning of the electrodes with respect to one another is necessary, so as to obtain, during recording of the copy, a homogeneous printing density in a plane, freedom from streaking and clean contours, in other words, a good quality of reproduction.
The counter electrodes disposed in another row extend also over the whole recording width. Each counter electrode is precisely aligned with a group of electrodes.
In order to create the necessary potential difference for a spark discharge, the electrodes and counter electrodes are fed by high voltage generators. Formation of these connections poses a particular problem when manufacturing the recording medium.
In German patents DT-OS No. 2 260 227, and DT-OS No. 2 261 529, there is already described a comb of electrodes, where the electrodes consist of individual wires embedded in plates of artificial resin.
In a comb of electrodes of this type, each electrode must be connected manually in a time consuming manner to an appropriate supply lead.
A comb of electrodes is known from German patent DT-OS No. 2,023,719, in which the electrodes are fabricated from conductive tracks on both sides of an insulating plate. The starting point therefor is a so-called doubly packed or lined foil, which is also used for printed circuits. This comb of electrodes also has the decided disadvantage, that the supply leads must be connected manually.
As there are a large number of electrodes in a comb of electrodes, the supply leads form a thick bundle of leads, which takes up a lot of space and is very difficult to manipulate or form.
A further disadvantage is due to the fact that in the aforesaid method of connection between the electrodes and the output circuit a replacement of the comb of electrodes is very time consuming and costly. Similar problems also arise for the arrangement of counter electrodes.
It is therefore one of the objects of the present invention to obviate these disadvantages, and to devise an electrostatic recording device having electrode- and counter-electrode means which is considerably simpler in construction, and which can be easily manufactured.